I think, there is a problem in the values assumed. For example, the amplitude is far greater than 1cm, lmao. In fact, it seemingly varies depending on how close people are to Senjumaru. For example, for Ichigo's party, the amplitude feels like almost 10 cm, for Kyoraku, it feels indeed like 1-2cm,and for isshin it looks like around 4-5 cm (considering the distance between the pov and him). Which doesn't make much sense given Isshin should be farther from her than Kyoraku.
I think the only way it makes sense is if we assume it feels the same everywhere, but varies in intensity between two given time intervals. In which case, we should still treat amplitude as being that shown from ichigo and his friends' pov, which, again, should be around 10 cm. It is crucial to consider, this is indeed but "the slightest use" of her true power and she should still scale above gremmy, but as others already said, that's another story. Here's the video: